1. Field of the Invention
The field of art to which this invention relates is broadcast television. It is more particularly directed to an apparatus and a method for coordinating the concurrent distribution of information sent over separate channels.
2. Description of Prior Art
Methods for the distribution of data are well known in the art. Clearly, data is distributed among the users of a local area network (LAN), and the same applies for a variety of network types. Capabilities for the broadcast distribution of data exist in the context of LANs as well as in other contexts, such as teletext systems.
Broadcast distribution systems may be used for the distribution of a variety of data types including text, graphics, video, and audio. However, the distribution of the data in these systems is not associated with a parallel broadcast of a video program.
Data carousel systems, such as the one described in U.S. Pat. No. 5,805,825, are designed to cyclically broadcast units of data to users. These systems, which may be analog or digital, may use video-related protocols and architectures for the transport of data on the carousel, but as above, the data distribution is not associated with a parallel broadcast of a video program on another channel.
Systems which are well known for the distribution of program scheduling information, in tandem with a video broadcast, are identified as Electronic or Interactive Program Guides (EPGs). Some systems for the distribution of EPG data, such as that described in U.S. Pat. No. 5,808,694 use a separate channel, such as a telephone line, into the Set-Top Box (STB) for downloading program information. Other systems, such as satellite digital video systems, use a cyclic periodic broadcast of program information.
Systems such as these do not require, or supply, a great deal of bandwidth for the data transport, since program information does not change frequently. A separate television channel is not used for the EPG data, since this would be a great waste of that channel""s bandwidth. That is because the EPG data consists of scheduling information for video programs, but is not coordinated with the actual content throughout that program.
Other systems for data distribution which are not coordinated with video, include U.S. Pat. No. 5,790,753, used for the download to STBs, of program software, and U.S. Pat. No. 5,341,474.
Set-top boxes are well known in the art. They may take analog input, or digital, or both. Since most monitors take analog input, even digital-input STBs have analog video and audio outputs. Examples of STBs are U.S. Pat. No. 5,734,853 having an analog/digital input, and U.S. Pat. No. 5,742,680 having digital input only. These referenced STBs do not extract data from an incoming broadcast stream.
Closed-caption information is commonly distributed along with the content of a video program, in the Vertical Blanking Interval (VBI) of an analog broadcast. This information is not closely synchronized with the video content. Additionally, only a small amount of data, roughly 200 Kbps, may be transported using VBI and architectural limitations prevent isochronous data from being transported using VBI.
Currently, a transition is in progress from analog television broadcasts, using broadcast standards such as NTSC to digital television broadcasts using broadcast standards such as ATSC. STBs are available to handle NTSC, ATSC, both ATSC and NTSC, or purely digital transmissions, such as those used for satellite distribution of digital television such as DVB in Europe and Australia or ARIB in Japan. However, even STBs which can handle analog and digital broadcasts do so in an either/or mannerxe2x80x94a channel is either analog or digital, and the content of an analog channel is not coordinated with the content of a digital channel.
What is needed is a system for the distribution of a high volume of data coordinated with the content of a video program where coordination includes matching data content to the video content throughout the program and a tight synchronization for the transport of isochronous data. That system may be used in the context of analog or digital television broadcasts, and in systems which are in transition between analog and digital modalities. An analog channel of that system may be used for both the transport of video and audio content as well as for the transport of information which may be used to coordinate the content of the analog channel with the content of another possibly digital-content channel.
The present invention uses multiple broadcast television channels to distribute high volume of data to a client device from a server. Multiple analog channels may be broadcast, at least one of which contains video/audio programs, and at least one separate channel contains data associated with channels containing those video/audio programs.
The channels containing the analog video/audio signal also contain control data inserted into the analog signal""s VBI. This channel""s content may be viewed using any conventional analog STB. STBs designed to implement this invention are equipped with at least two tuners in order to tune to two of those channels simultaneously. One tuner is used to tune to the video/audio channel, and extract the control data in the VBI. The second tuner is used to tune to the channel containing the data itself, a digital data stream which is modulated onto an analog channel.
The control data extracted from the video/audio channel contains pointers to the data units available on the data channel. When the user requests access to supplementary data, e.g., by replying to an on-screen notification that data is available, the STB uses the control data to locate and access the data on the data channel. The supplementary data may be closely associated with the content of the video channel and can be tightly synchronized with that content.
Some of the advantages of this data distribution system include:
(1) the high volume of data which can be delivered, in contrast with the low bandwidth available with analog data distribution systems such as those using VBI only;
(2) the compatibility of this system with existing analog broadcast systems and STB""s, and
(3) the migration path this system provides as broadcast systems move from analog to digital.